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Lesson 4 of 10

5 min

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A pond turns brown after rain. By the next morning, the water on top looks clear.

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Muddy water, freshly stirred. Mud is everywhere.
Step 1 of 4
  1. Muddy water, freshly stirred. Mud is everywhere.
  2. Left still. The heavy mud starts to sink.
  3. Mud rests at the bottom. Clear water sits on top.
  4. Tip carefully. The clear water pours off.

The rule

Sedimentation — heavy bits sinking to the bottom when left still.

Decantation — pouring off the clear water on top, slowly.

Only solids that do not dissolve can settle.

Salt in water is dissolved: you cannot see it. Its tiny pieces do not sink.

Try the lab to finish this lesson.